Common Bird’s-nest Fungus, Crucibulum laeve, growing in our greenhouse.

A week ago I cleared the last tomato plants out of our greenhouse in the back garden and brought the last green tomatoes indoors to ripen (note 1). As I pulled up the tomato plants, I had a lovely surprise: a little cluster of bird’s-nest fungi on the soil.

Bird’s-nest fungi have fruiting bodies that resemble tiny birds’ nests, complete with eggs. The fungi feed on decaying organic matter and can be found on soils containing plant debris such as little twigs, on wood chip and bark mulch, or growing on decaying wood.

Bird’s-nest fungi are members of the family Nidulariaceae (nidulus means small nest), part of the order Agaricales, which includes familiar species of fungi such as cultivated mushrooms (Agaricus bisporus) and  well-known wild species such as Shaggy Inkcap (Coprinus comatus, which I have already written about) and Fly Agaric (Amanita muscaria).

Worldwide, there are five genera of fungi in the Nidulariaceae: Crucibulum, Cyathus, Nidularia, Mycocalia, and Nidula (note 2).

The species I found in the greenhouse was the Common Bird’s-nest Fungus, Crucibulum laeve, one of the most common species. It can usually be found growing in small clusters in late autumn and winter. (I counted nine fruit bodies, growing singly or in small groups.)

Common Bird’s Nest fungi are found through much of the British Isles and in mainland Europe and Asia, as well other temperate areas, including many parts of North America. They are probably overlooked due to their small size and the way they blend with their background – I like to think I am observant, but it didn’t spot them until I’d nearly finished work in the greenhouse.

To start with, the fungus’ cups are covered in a fragile yellowish membrane, known as the epiphragm. This soon breaks apart as the fruit body expands to form the “nest” –  a cup that contains a number of small white “eggs” (note 3). These are actually spore packets, known as peridioles. Each peridiole is attached to the the cup wall by a thread known as a funiculus.

Three young specimens of Common Bird’s-nest Fungus, Crucibulum laeve. In the lower two the epiphragm is just starting to break.

The peridioles of bird’s-nest fungi are spread by the splashing of raindrops, which fall into the cup and send them flying. The attached funiculus helps the periodiole on its journey and when it lands may coil around a grass stem, preventing further flight. Ideally a passing grazing animal will then eat the grass and the periodiole will pass through the animal’s body unharmed and arrive in a new location in a parcel of nutritious dung. In the greenhouse any water drops will come from my watering can and there aren’t any grazing animals (unless you count slugs, snails or woodlice) but the fungi should disperse their spores just fine (note 4).

Other types of bird’s-nest fungi you may find in Britain include the following:

• Field Bird’s-nest, Cyathus olla. Widespread and common, especially on woodchip mulch. It has dark grey peridioles.
• Fluted Bird’s-nest, Cyathus striatus. Widespead and fairly common, on twigs and woody debris. Pale grey peridioles in a fluted goblet.
• Dung Bird’s-nest, Cyathus stercoreus. Very rare, on rabbit dung in sand dunes, found in Wales and Galloway in southern Scotland. Black peridioles.
• Pea-shaped Bird’s nest, Nidularia deformis. Widespread but uncommon, on fallen branches, twigs and woody debris as well as woodchip. Chestnut-brown peridioles, embedded in sticky mucilage, without a funicular cord.

This autumn I’ve also seen Field Bird’s-nest and Fluted Bird’s-nest in Norwich, but I have never encountered Dung Bird’s-nest or Pea-shaped Bird’s-nest.

Field Bird’s-nest, Cyathus olla

Fluted Bird’s-nest, Cyathus striatus. Taken in low light conditions, this is not the best of pictures, but the fluting inside the cup makes the fungus easily recognisable.

Notes

Note 1 – If any tomatoes are stubborn to ripen I will put them in a paper bag or shoe box with a banana. This will eventually sacrifice the banana, but the ethylene gas it gives off will help to ripen the tomatoes.

Note 2 – In Britain, you are most likely to encounter members of the first three genera, although the NBN Atlas lists 144 records for Mycocalia denudata at the time of writing. It is a tiny member of the family. In Germany it has been recorded from decaying plant remains and also on rabbit and sheep dung. In New Brunswick (Canada) it has been recorded on lemming dung. There are photographs of Mycocalia denudata on both these websites.

There are five species of Nidula worldwide, which can be found in North America, Japan, the Himalayas and parts of the Caribbean, but not in Britain.

Note 3 – The First Nature website says that the cup contains 5 – 10 “eggs” (peridioles) but Geoffrey Kibby, in his book “Mushrooms and Toadstools of Britain and Europe, Volume 1” (2017)  says that the number ranges from 10 – 15, with sometimes as many as 20 per cup. Sterry and Hughes say 10 -15. I counted eleven “eggs” in one of my smaller specimens.

Kibby gives Crucibulum laeve the more descriptive English name of White-egg Bird’s-nest; Common Bird’s-nest is used more generally, including in Sterry and Hughes in “Collins Complete Guide to British Mushrooms and Toadstools” (2009).

Crucibulum means crucible and laeve means smooth.

Note 4 – The New Brunswick Museum web page on Bird’s-nest Fungi cites some fascinating work that was done on artificial bird’s-nest fungi, described in Harold Brodie’s book “The Bird’s Nest Fungi” (University of Toronto Press, 1975). Brodie and Buller found that the angle of the cup walls is critical to the distance the peridioles can travel. “Too great or too little an angle and they will not travel as far. The ideal angle for dispersal by large raindrops having a terminal velocity of 4-8 meters per second is between 60 and 70 degrees with the horizontal.”